This is a very strange problem.

I have a server running Server 2008 (Web Edition). It has two NICS in it. One is connected to a local LAN, the other to a router/firewall on the Internet.

This scenario has been working fine for the past year with users on the local LAN able to access the Internet by pointing their browsers to a proxy server on the 2008 server which bridges across the two NICS.

We put in a new router to provide more functionality. It didn't work out so we removed it and put back the existing router.  In the interim we had to reboot the server and more than once renew the lease on each of the NICS.

Now users can still access the Internet as before but we have a strange problem that when we are on the server, we can ping/access workstations/servers on the local subnet that the 2008 server is on, but we cannot see servers in a different subnet we could see before. So our server is on 172.59.* and can see all workstations and servers in that subnet. But it cannot see anything in the 172.22.* subnet even though DHCP has assigned a gateway in the 172.22 subnet.

But if we disable the external NIC we can now see all servers on both subnets but of course external Internet access is lost.

Can anybody think what might cause this problem and where we should look?

Thanks